Microsoft Defender for Office 365 vs OpenText Email Security: Side-by-Side Comparison (2026)

Microsoft Defender for Office 365

Mid-market and enterprise teams already operating Microsoft 365 should standardize on Defender for Office 365 because the integration depth eliminates the detection gaps that plague bolt-on email security tools, particularly in Teams and SharePoint where most modern attacks now land. The platform's automated Business Email Compromise disruption with user disabling and device isolation actually stops lateral movement in real time rather than just flagging suspicious mail. Skip this if your organization runs primarily on Gmail or Slack; the advantage collapses outside the Microsoft ecosystem, and you'll find cheaper, more agile options elsewhere.

OpenText Email Security

Mid-market and enterprise teams handling regulated data will find real value in OpenText Email Security's automatic encryption and DLP filters, which actually prevent exfiltration rather than just flag it. The platform covers both inbound threat detection and outbound data loss in a single console, and its email continuity feature keeps you operational when other vendors go dark. Skip this if your organization needs integrated endpoint detection or advanced sandbox detonation; OpenText prioritizes encryption and policy enforcement over behavioral threat hunting.